Cycles rendering objects all black
I think what happened here was just a misclick in your render layer settings. It looks like you accidentally added a layer as a mask layer.

What is a mask layer

A mask layer is a layer that is used as a mask to turn parts of a renderlayer transparent depending on if anything (that appears in the render) is infront of something from that renderlayer.

What's the issue?

Your issue, is that you have your first layer (the one that has all your objects on it), set to be a mask layer, so essentially what is happening, is that instead of rendering the objects, there shape is filled with transparency. I just doesn't appear transparent because you don't have film transparent checked.

To fix this, simply uncheck that layer from the mask layers.